| This study aimed at assessing the fate and ecotoxicology of two newly introduced pesticides- a herbicide cyhalofop butyl (XDE-537) and an insecticide Profurite aminium, in the paddy rice ecosystem. To achieve this, experiments were carried in the green house for the fate studies and in the laboratory to determine the subtethal effects of the pesticides on selected fish species. A herbicide formulation Clincher 100EC containing cyhatofop butyl (100g a.i/L) as the active ingredient and the insecticide formulation Profurite aminium 78%SP (780g a.i/kg) were used as the test chemicals. The fate study focused on the dissipation dynamics of the two pesticides. The times of disappearance (DT) from the system of cyhatofop butyl and its metabolites ACID, AMIDE, DIACID and DP and the nereistoxin (insecticida! component of Profurite aminium) after application were determined. Ecotoxcotogical investigation employed in vivo experiments on biochemical responses of two fish species, goldfish (Carassius auratus) and Topmouth gudgeon (Pseudorasbora pan/a). Genotoxicity (only for Topmouth gudgeon) was also investigated as part of ecotoxicological studies with respect to the test chemicals. Four kinds of enzymes: Glutathione-S-transferase (GST), Liver esterases, Acetylcholinesterase (AchE) and Mixed function oxidases (MFOs) including aldrin epoxidase and ethoxyresorufin-O deethyiase (EROD) were covered under biochemical tests following 96h exposure to the chemicals. Genotoxicity on the other hand, covered three aspects: DMA strand damage, unscheduled DMA synthesis (UDS) and DNA methylation. In all experiments, two levels of closes, low and high were applied for pesticide treatments including the mixed one (herbicide + Insecticide). The treatments were designated as C for clincher, and P for Profurite aminium. Subscript land 2 meant tow and high doses, respectively. The doses used for fate studies were 2xfiekj rate (PR) [tow] and 20x FR (high). The doses for enzyme and genotoxicity tests were 10% (tow) and 20% (high) of the LD50 values obtained in minor toxicity experiments that were carried prior to the commencing of this study.The results indicated that cyhatofop butyl disappeared very fast in water. Rate of disappearance from the components studied were in the order water>Soil>rice straw. This pattern differed slightly from that of Nereistoxin, a component of Profurite aminium whose disappearance ,followed the order Wateorice straw > soil. Overall, both Profurite aminium and Clincher and their degradation products were found to have fairly short disappearance time (DT). The DT?values in water were 0.14, 0.67, 7.64 and 1.3 days for XDE-537, ACID, AMIDE and Profurite aminium respectively. In soil the values were 6.72,7,04, 0.96 and 9.3 for ACID, DIACID, AMIDE and Profurite aminium respectively. In rice straw DT50 values were 2.27,4.28 and 5.3 days for XDE-537, ACID and Profurite aminium respectively. Cyhatofop butyl and its metabolites and Profurite aminium were thus concluded to be non-persistentFollowing the biochemical tests, GST was found to be induced in both Goldfish and topmouth gudgeon1)y the insecticide Profurite aminium. Clincher only caused GST induction in topmouth gudgeon. The mixed treatment (CP) had the highest effect in topmouth gudgeon {722.3 nmol/min/mg protein) with a possible indication of additive toxicity (C alone had a maximum activity of 285.2 nmol/min/mg protein and P had an activity of 414.0 nmol/min/mg protein). The inherent GST activity for the two fish species was much higher in goldfish (1681.4 nmol/min/mg protein) than topmouth gudgeon 78.3 nmol/min/mg protein).Liver esterases were induced by both Clincher 100EC and Profurite aminium in Goldfish. In Topmouth gudgeon liver esterases were induced only by Profurite aminium but inhibited by Clincher 100EC. The baseline activities for the unexposed fish was higher in topmouth gudgeon (395.8 nmol/min/mg protein) than goldfish 259.8 nmol/min/mg protein.AchE of topmouth gudgeon was found to be inhibited by both Clincher and Profurite aminium...
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